Didn't the OP also put in a TM40 before this happened? more torque / power than the drivetrain can handle?
I know i'm grasping at straws but you gotta think If nothing's changed on these bikes since 97 and this is a more recent occurance then something new has been thrown into the mix.

DJ'd stock carb.

So far it's bikes from 99-05 that have blown. They changed the gear part number in '06.

Quote:

Originally Posted by plugeyes

the power increase isnt enough to make any difference design-wise.
look at the logistics, most are australian & new zealand. that could be significant.

But in NZ half the bikes we get are US spec.
The '97 I bought to nick the engine from is a US one.